The patch titled
sysctl: use RCU strings for core_pattern sysctl
has been added to the -mm tree. Its filename is
sysctl-use-rcu-strings-for-core_pattern-sysctl.patch
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The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/
------------------------------------------------------
Subject: sysctl: use RCU strings for core_pattern sysctl
From: Andi Kleen <andi@xxxxxxxxxxxxxx>
Also saves ~220 bytes in the data segment for default kernels.
As a bonus this removes one use of the BKL.
Signed-off-by: Andi Kleen <ak@xxxxxxxxxxxxxxx>
Cc: "Paul E. McKenney" <paulmck@xxxxxxxxxx>
Cc: Russell King <rmk+lkml@xxxxxxxxxxxxxxxx>
Cc: Sam Ravnborg <sam@xxxxxxxxxxxx>
Cc: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>
Cc: Rusty Russell <rusty@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/exec.c | 11 +++++------
kernel/sysctl.c | 6 +++---
2 files changed, 8 insertions(+), 9 deletions(-)
diff -puN fs/exec.c~sysctl-use-rcu-strings-for-core_pattern-sysctl fs/exec.c
--- a/fs/exec.c~sysctl-use-rcu-strings-for-core_pattern-sysctl
+++ a/fs/exec.c
@@ -62,7 +62,7 @@
#include "internal.h"
int core_uses_pid;
-char core_pattern[CORENAME_MAX_SIZE] = "core";
+char *core_pattern = "core";
unsigned int core_pipe_limit;
int suid_dumpable = 0;
@@ -1422,7 +1422,7 @@ EXPORT_SYMBOL(set_binfmt);
static int format_corename(char *corename, long signr)
{
const struct cred *cred = current_cred();
- const char *pat_ptr = core_pattern;
+ const char *pat_ptr = rcu_dereference(core_pattern);
int ispipe = (*pat_ptr == '|');
char *out_ptr = corename;
char *const out_end = corename + CORENAME_MAX_SIZE;
@@ -1838,12 +1838,11 @@ void do_coredump(long signr, int exit_co
clear_thread_flag(TIF_SIGPENDING);
/*
- * lock_kernel() because format_corename() is controlled by sysctl, which
- * uses lock_kernel()
+ * Protect corename by RCU vs proc_rcu_string()
*/
- lock_kernel();
+ rcu_read_lock();
ispipe = format_corename(corename, signr);
- unlock_kernel();
+ rcu_read_unlock();
if ((!ispipe) && (cprm.limit < binfmt->min_coredump))
goto fail_unlock;
diff -puN kernel/sysctl.c~sysctl-use-rcu-strings-for-core_pattern-sysctl kernel/sysctl.c
--- a/kernel/sysctl.c~sysctl-use-rcu-strings-for-core_pattern-sysctl
+++ a/kernel/sysctl.c
@@ -75,7 +75,7 @@ extern int sysctl_oom_dump_tasks;
extern int max_threads;
extern int core_uses_pid;
extern int suid_dumpable;
-extern char core_pattern[];
+extern char *core_pattern;
extern unsigned int core_pipe_limit;
extern int pid_max;
extern int min_free_kbytes;
@@ -399,10 +399,10 @@ static struct ctl_table kern_table[] = {
},
{
.procname = "core_pattern",
- .data = core_pattern,
+ .data = &core_pattern,
.maxlen = CORENAME_MAX_SIZE,
.mode = 0644,
- .proc_handler = proc_dostring,
+ .proc_handler = proc_rcu_string,
},
{
.procname = "core_pipe_limit",
_
Patches currently in -mm which might be from andi@xxxxxxxxxxxxxx are
kernel-signalc-fix-kernel-information-leak-with-print-fatal-signals=1.patch
proc-revert-procfs-provide-stack-information-for-threads.patch
kfifo-use-void-pointers-for-user-buffers.patch
kfifo-sanitize-_user-error-handling.patch
kfifo-add-kfifo_out_peek.patch
kfifo-add-kfifo_initialized.patch
kfifo-document-everywhere-that-size-has-to-be-power-of-two.patch
hardware-latency-detector-remove-default-m.patch
kbuild-move-fno-dwarf2-cfi-asm-to-powerpc-only.patch
mm-introduce-dump_page-and-print-symbolic-flag-names.patch
coredump-unify-dump_seek-implementations-for-each-binfmt_c.patch
coredump-move-dump_write-and-dump_seek-into-a-header-file.patch
elf-coredump-replace-elf_core_extra_-macros-by-functions.patch
elf-coredump-make-offset-calculation-process-and-writing-process-explicit.patch
elf-coredump-add-extended-numbering-support.patch
tracehooks-kill-some-pt_ptraced-checks.patch
tracehooks-check-pt_ptraced-before-reporting-the-single-step.patch
ptrace_signal-check-pt_ptraced-before-reporting-a-signal.patch
export-__ptrace_detach-and-do_notify_parent_cldstop.patch
reorder-the-code-in-kernel-ptracec.patch
implement-utrace-ptrace.patch
utrace-core.patch
rcu-add-rcustring-adt-for-rcu-protected-strings.patch
add-a-kernel_address-that-works-for-data-too.patch
sysctl-add-proc_rcu_string-to-manage-sysctls-using-rcu-strings.patch
sysctl-use-rcu-strings-for-core_pattern-sysctl.patch
sysctl-add-call_usermodehelper_cleanup.patch
sysctl-convert-modprobe_path-to-proc_rcu_string.patch
sysctl-convert-poweroff_command-to-proc_rcu_string.patch
sysctl-convert-hotplug-helper-string-to-proc_rcu_string.patch
sysctl-use-rcu-protected-sysctl-for-ocfs-group-add-helper.patch
--
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